Hi Li and others,
You are right that the system is probably too new to be operative in any lab yet – if any is already sold.... Setting up such a system certainly will take some time before producing ‘routine’ data. Let us invite the first users to report their experiences to the list.
About your statement on the good precision I think this is highly disputable as it is presented many times nowadays (also true for GC-IRMS or for some other methods). The given ‘precision’ is only part of the combined uncertainty as properly should be given. What is done is giving a final delta value, generally with proper corrections on the delta value, but only with the uncertainty of the last part of the analytical procedure. Uncertainties of, for instance, the standard (or working reference) and on the ‘preparation’ of the sample are omitted (or simply forgotten), thus producing a too optimistic uncertainty (just the statistical SD of the IRMS measurement in most cases). This is even worse with hydrogen, where the (relatively huge) uncertainty on the H3+ correction is left out completely...
Specially if the results are used for interpretations based on small isotopic variations this can give erroneous conclusions, such as for (paleo-)thermometry, to name one case.
There is a strange tendency where the analyst giving the smallest precisions is considered the best one... (I call it the ‘Guiness Book of Records’ tendency). It would be better to consider those analysts reporting ‘realistic’ combined uncertainties as more reliable! We have seen such strange tendencies also for radiometric age dating. Those measuring the oldest ages (oldest rock) received more ‘appreciation’ than those giving the proper age of a rock (a rock is as old as it is... and giving the correct age in the proper way is the only importance here! Nice to have the oldest rock, but it is not of importance for the measurement procedure or the quality of the analyst at all).
I discussed this topic also with Andreas Hilkert some time ago. I like to add that it is not my aim to point my finger towards any company or a particular person. This , to my opinion, erroneous (or incomplete..) reporting of uncertainties has become very common by now.
Accuracy is another story...
Best wishes,
Pier.
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Dr. Pier A. de Groot
Pastoor Moorkensstraat 16
2400 Mol - Achterbos
Belgium
Tel. +32 (0)14 326 205
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Visit my WEB-site about my “Handbook of Stable Isotope Analytical Techniques” at:
http://users.pandora.be/handbook/index.html
last update: 17 Maart, 2004.
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